diff --git a/packages/coding-agent/package.json b/packages/coding-agent/package.json
index 5f000f7ed..43b41d915 100644
--- a/packages/coding-agent/package.json
+++ b/packages/coding-agent/package.json
@@ -35,8 +35,8 @@
 		"dev": "tsgo -p tsconfig.build.json --watch --preserveWatchOutput",
 		"build": "tsgo -p tsconfig.build.json && shx chmod +x dist/cli.js && npm run copy-assets && npm run bundle",
 		"build:binary": "npm --prefix ../tui run build && npm --prefix ../ai run build && npm --prefix ../agent run build && npm run build && bun build --compile ./dist/bun/cli.js --outfile dist/pi && npm run copy-binary-assets",
-		"copy-assets": "shx mkdir -p dist/modes/interactive/theme && shx cp src/modes/interactive/theme/*.json dist/modes/interactive/theme/ && shx mkdir -p dist/modes/interactive/assets && shx cp src/modes/interactive/assets/*.png dist/modes/interactive/assets/ && shx mkdir -p dist/core/export-html/vendor && shx cp src/core/export-html/template.html src/core/export-html/template.css src/core/export-html/template.js dist/core/export-html/ && shx cp src/core/export-html/vendor/*.js dist/core/export-html/vendor/ && shx rm -rf dist/prime-agent-runtime && shx cp -r ../../prime-agent-runtime dist/prime-agent-runtime",
-		"copy-binary-assets": "shx cp package.json dist/ && shx cp README.md dist/ && shx cp CHANGELOG.md dist/ && shx mkdir -p dist/theme && shx cp src/modes/interactive/theme/*.json dist/theme/ && shx mkdir -p dist/assets && shx cp src/modes/interactive/assets/*.png dist/assets/ && shx mkdir -p dist/export-html/vendor && shx cp src/core/export-html/template.html dist/export-html/ && shx cp src/core/export-html/vendor/*.js dist/export-html/vendor/ && shx cp -r docs dist/ && shx cp -r examples dist/ && shx cp -r skills dist/ && shx cp ../../node_modules/@silvia-odwyer/photon-node/photon_rs_bg.wasm dist/",
+		"copy-assets": "shx mkdir -p dist/modes/interactive/theme && shx cp src/modes/interactive/theme/*.json dist/modes/interactive/theme/ && shx mkdir -p dist/modes/interactive/assets && shx cp src/modes/interactive/assets/*.png dist/modes/interactive/assets/ && shx mkdir -p dist/core/export-html/vendor && shx cp src/core/export-html/template.html src/core/export-html/template.css src/core/export-html/template.js dist/core/export-html/ && shx cp src/core/export-html/vendor/*.js dist/core/export-html/vendor/ && shx rm -rf dist/prime-agent-runtime && shx cp -r ../../prime-agent-runtime dist/prime-agent-runtime && shx rm -rf dist/skills && shx cp -r skills dist/skills",
+		"copy-binary-assets": "shx cp package.json dist/ && shx cp README.md dist/ && shx cp CHANGELOG.md dist/ && shx mkdir -p dist/theme && shx cp src/modes/interactive/theme/*.json dist/theme/ && shx mkdir -p dist/assets && shx cp src/modes/interactive/assets/*.png dist/assets/ && shx mkdir -p dist/export-html/vendor && shx cp src/core/export-html/template.html dist/export-html/ && shx cp src/core/export-html/vendor/*.js dist/export-html/vendor/ && shx cp -r docs dist/ && shx cp -r examples dist/ && shx cp ../../node_modules/@silvia-odwyer/photon-node/photon_rs_bg.wasm dist/",
 		"test": "vitest --run",
 		"postinstall": "node postinstall.cjs",
 		"prepublishOnly": "npm run clean && npm run build",
diff --git a/packages/coding-agent/src/core/package-manager.ts b/packages/coding-agent/src/core/package-manager.ts
index f7ed1d843..db4e9d205 100644
--- a/packages/coding-agent/src/core/package-manager.ts
+++ b/packages/coding-agent/src/core/package-manager.ts
@@ -31,6 +31,7 @@ import { CONFIG_DIR_NAME, getBundledSkillsDir } from "../config.js";
 import { shouldUseWindowsShell } from "../utils/child-process.js";
 import { type GitSource, parseGitUrl } from "../utils/git.js";
 import { canonicalizePath, isLocalPath } from "../utils/paths.js";
+import type { ResourceDiagnostic } from "./diagnostics.js";
 import { isStdoutTakenOver } from "./output-guard.js";
 import type { PackageSource, SettingsManager } from "./settings-manager.js";
 
@@ -62,6 +63,7 @@ export interface ResolvedPaths {
 	skills: ResolvedResource[];
 	prompts: ResolvedResource[];
 	themes: ResolvedResource[];
+	diagnostics: ResourceDiagnostic[];
 }
 
 export type MissingSourceAction = "install" | "skip" | "error";
@@ -158,6 +160,7 @@ interface ResourceAccumulator {
 	skills: Map<string, { metadata: PathMetadata; enabled: boolean }>;
 	prompts: Map<string, { metadata: PathMetadata; enabled: boolean }>;
 	themes: Map<string, { metadata: PathMetadata; enabled: boolean }>;
+	diagnostics: ResourceDiagnostic[];
 }
 
 /**
@@ -2242,13 +2245,20 @@ export class DefaultPackageManager implements PackageManager {
 				origin: "top-level",
 				baseDir: this.bundledSkillsDir,
 			};
-			addResources(
-				"skills",
-				collectAutoSkillEntries(this.bundledSkillsDir, "pi"),
-				builtinMetadata,
-				userOverrides.skills,
-				this.bundledSkillsDir,
-			);
+			const builtinEntries = collectAutoSkillEntries(this.bundledSkillsDir, "pi");
+			// Built-in skills (edit, goal, …) are expected to ship with the package. A
+			// packaging slip that drops the skills/ dir from the build output would
+			// otherwise degrade silently to zero skills (ENG-4220); surface it loudly.
+			if (builtinEntries.length === 0) {
+				accumulator.diagnostics.push({
+					type: "warning",
+					message: existsSync(this.bundledSkillsDir)
+						? "built-in skills directory contains no skills; this build may be packaged incorrectly"
+						: "built-in skills directory not found; this build may be packaged incorrectly",
+					path: this.bundledSkillsDir,
+				});
+			}
+			addResources("skills", builtinEntries, builtinMetadata, userOverrides.skills, this.bundledSkillsDir);
 		}
 		addResources(
 			"prompts",
@@ -2321,6 +2331,7 @@ export class DefaultPackageManager implements PackageManager {
 			skills: new Map(),
 			prompts: new Map(),
 			themes: new Map(),
+			diagnostics: [],
 		};
 	}
 
@@ -2349,6 +2360,7 @@ export class DefaultPackageManager implements PackageManager {
 			skills: mapToResolved(accumulator.skills),
 			prompts: mapToResolved(accumulator.prompts),
 			themes: mapToResolved(accumulator.themes),
+			diagnostics: accumulator.diagnostics,
 		};
 	}
 
diff --git a/packages/coding-agent/src/core/resource-loader.ts b/packages/coding-agent/src/core/resource-loader.ts
index 8ac486737..7ccc896e4 100644
--- a/packages/coding-agent/src/core/resource-loader.ts
+++ b/packages/coding-agent/src/core/resource-loader.ts
@@ -425,6 +425,8 @@ export class DefaultResourceLoader implements ResourceLoader {
 
 		this.lastSkillPaths = skillPaths;
 		this.updateSkillsFromPaths(skillPaths, metadataByPath);
+		// Surface resolution-time skill warnings (e.g. missing bundled skills dir).
+		this.skillDiagnostics.push(...resolvedPaths.diagnostics);
 		for (const p of this.additionalSkillPaths) {
 			if (isLocalPath(p) && !existsSync(p) && !this.skillDiagnostics.some((d) => d.path === p)) {
 				this.skillDiagnostics.push({ type: "error", message: "Skill path does not exist", path: p });
diff --git a/packages/coding-agent/test/builtin-skills.test.ts b/packages/coding-agent/test/builtin-skills.test.ts
index e3df4c2aa..768ef0982 100644
--- a/packages/coding-agent/test/builtin-skills.test.ts
+++ b/packages/coding-agent/test/builtin-skills.test.ts
@@ -98,6 +98,61 @@ describe("builtin skills", () => {
 			expect(result.skills.some((r) => r.metadata.source === "builtin")).toBe(false);
 		});
 
+		it("warns when the bundled skills directory is missing (packaging slip)", async () => {
+			const missingDir = join(tempDir, "does-not-exist");
+			const packageManager = new DefaultPackageManager({
+				cwd,
+				agentDir,
+				settingsManager,
+				bundledSkillsDir: missingDir,
+			});
+			const result = await packageManager.resolve();
+
+			const warning = result.diagnostics.find((d) => d.path === missingDir && d.type === "warning");
+			expect(warning).toBeDefined();
+			expect(warning?.message).toContain("built-in skills");
+		});
+
+		it("warns when the bundled skills directory exists but is empty", async () => {
+			const packageManager = new DefaultPackageManager({
+				cwd,
+				agentDir,
+				settingsManager,
+				bundledSkillsDir: bundledDir,
+			});
+			const result = await packageManager.resolve();
+
+			const warning = result.diagnostics.find((d) => d.path === bundledDir && d.type === "warning");
+			expect(warning).toBeDefined();
+		});
+
+		it("does not warn when bundled skills are present", async () => {
+			writeSkill(bundledDir, "builtin-skill");
+			const packageManager = new DefaultPackageManager({
+				cwd,
+				agentDir,
+				settingsManager,
+				bundledSkillsDir: bundledDir,
+			});
+			const result = await packageManager.resolve();
+
+			expect(result.diagnostics.some((d) => d.path === bundledDir)).toBe(false);
+		});
+
+		it("does not warn when built-in skills are disabled", async () => {
+			const missingDir = join(tempDir, "does-not-exist");
+			settingsManager.setEnableBuiltinSkills(false);
+			const packageManager = new DefaultPackageManager({
+				cwd,
+				agentDir,
+				settingsManager,
+				bundledSkillsDir: missingDir,
+			});
+			const result = await packageManager.resolve();
+
+			expect(result.diagnostics.some((d) => d.path === missingDir)).toBe(false);
+		});
+
 		it("disables individual bundled skills via settings override patterns", async () => {
 			writeSkill(bundledDir, "builtin-skill");
 			writeSkill(bundledDir, "other-skill");
@@ -151,6 +206,15 @@ describe("builtin skills", () => {
 
 			expect(loader.getSkills().skills).toEqual([]);
 		});
+
+		it("surfaces a skill diagnostic when the bundled skills dir is missing", async () => {
+			const missingDir = join(tempDir, "does-not-exist");
+			const loader = new DefaultResourceLoader({ cwd, agentDir, bundledSkillsDir: missingDir });
+			await loader.reload();
+
+			const { diagnostics } = loader.getSkills();
+			expect(diagnostics.some((d) => d.path === missingDir && d.type === "warning")).toBe(true);
+		});
 	});
 
 	describe("shipped skill content", () => {
@@ -214,4 +278,33 @@ describe("builtin skills", () => {
 			expect(skills[0].kind === "python" && skills[0].python.importName).toBe("word_count");
 		});
 	});
+
+	// The bundled skills only reach a deployed agent if the build/release scripts
+	// copy skills/ into the shipped layout. A regression here resolves zero
+	// built-in skills at runtime even though the source tree looks correct
+	// (ENG-4220), so assert each shipping path still copies skills.
+	describe("packaging ships bundled skills", () => {
+		const packageRoot = join(__dirname, "..");
+		const repoRoot = join(packageRoot, "..", "..");
+
+		it("npm build (copy-assets) copies skills into dist", () => {
+			const pkg = JSON.parse(readFileSync(join(packageRoot, "package.json"), "utf-8")) as {
+				files?: string[];
+				scripts?: Record<string, string>;
+			};
+			expect(pkg.scripts?.["copy-assets"]).toContain("skills dist/skills");
+			// npm publish ships the source skills/ dir via the files allowlist too.
+			expect(pkg.files).toContain("skills");
+		});
+
+		it("binary release script copies skills next to the executable", () => {
+			const script = readFileSync(join(repoRoot, "scripts", "build-binaries.sh"), "utf-8");
+			expect(script).toMatch(/cp -r skills binaries\/\$platform\//);
+		});
+
+		it("release packer includes skills in the packed package", () => {
+			const script = readFileSync(join(repoRoot, "scripts", "pack-prime-agent-release.mjs"), "utf-8");
+			expect(script).toContain('"skills"');
+		});
+	});
 });
diff --git a/scripts/build-binaries.sh b/scripts/build-binaries.sh
index 635aca64f..cbc029f81 100755
--- a/scripts/build-binaries.sh
+++ b/scripts/build-binaries.sh
@@ -128,6 +128,7 @@ for platform in "${PLATFORMS[@]}"; do
     cp -r dist/core/export-html binaries/$platform/
     cp -r docs binaries/$platform/
     cp -r examples binaries/$platform/
+    cp -r skills binaries/$platform/
 
     # Copy koffi native module for Windows (needed for VT input support)
     if [[ "$platform" == "windows-x64" ]]; then
diff --git a/scripts/pack-prime-agent-release.mjs b/scripts/pack-prime-agent-release.mjs
index a3fa84d18..4d419fec0 100644
--- a/scripts/pack-prime-agent-release.mjs
+++ b/scripts/pack-prime-agent-release.mjs
@@ -196,7 +196,7 @@ function copyPackageContents(sourceDir, targetDir, packageJson) {
 	mkdirSync(targetDir, { recursive: true });
 	writeJson(join(targetDir, "package.json"), packageJson);
 
-	for (const entry of ["dist", "docs", "examples", "postinstall.cjs", "README.md", "CHANGELOG.md"]) {
+	for (const entry of ["dist", "docs", "examples", "skills", "postinstall.cjs", "README.md", "CHANGELOG.md"]) {
 		copyIfExists(join(sourceDir, entry), join(targetDir, entry));
 	}
 }